The last major fish kill happened in August 2012. In the past eleven years, eight fish kill incidents have been reported to the Guam Department of Agriculture. These incidents happen almost annually during the late summer. Many of these situations have been reported by members of the general public.

When a fish kill is reported, biologists or technicians are sent to the scene to investigate. Based on their reports, the Guam Department of Agriculture reports that a majority of these incidents have happened in July and August when low tides occur in the middle of the day. Extremely low tides in the afternoon can cause water temperature to increase, which can affect fish. July and August are also during rainy season. Large amounts of freshwater can also affect fish by quickly changing the salinity, turbidity and temperature of water.